<html>
<head>
<script type="text/javascript" src="../script/jquery.js"></script>
<script type="text/javascript">
$(document).ready(function(){
  $(".btn1").click(function(){
  $("p").slideToggle();
  });
});
</script>
</head>
<body>
<p>This is a paragraph.</p>
<button class="btn1">Toggle</button>
</body>
</html>